What’s the Matter Chemistry is the study of matter and the transformations it can undergo…

transcript

What’s the Matter

Chemistry is the study of matter and the transformations it can

undergo…

Chemistry is the study of matter and the transformations it can

undergo…

…. Matter is anything that occupies space.

Guiding QuestionsWhy do substances boil or freeze at different temperatures? Why do we put salt on the roads in the winter?

What properties of diamonds make them useful in a variety of applications?

Classification of Matter

• Scientists classify or group materials based on different characteristics. Matter can be classified according to whether it is a mixture or a pure substance.

MATTER

Can it be physically separated?

Homogeneous Mixture

(solution)

Heterogeneous Mixture Compound Element

MIXTURE PURE SUBSTANCE

yes no

Can it be chemically decomposed?

noyesIs the composition uniform?

Colloids Suspensions

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Particle Theory of Matter

• All matter is made up of tiny particles

• Each pure substance has its own kind of particle, which is different from the particles of other pure substances.

• Particles attract each other• Particles are always moving.• Particles at a higher

temperature move faster, on average, than particles at a lower temperature.

ions Water molecules

Pure Substances

• Contain only one kind of particle.

• e.g. water, oxygen gas, chlorine gas, sodium metal.

• Can be classified into two main groups: elements and compounds. Sulphur on the left is composed of one type

of atom, and water on the right is made up of a compound, with 1 type of molecule (2 hydrogen and 1 oxygen atom).

Pure Substances

Element– composed of identical atoms– EX: copper wire, aluminum foil

Pure Substances

Compound

– composed of 2 or more elements in a fixed ratio

– properties differ from those of individual elements

– EX: table salt (NaCl)

Pure Substances

Law of Definite CompositionLaw of Definite Composition

– A given compound always contains the same, fixed ratio of elements.

Law of Multiple ProportionsLaw of Multiple Proportions

– Elements can combine in different ratios to form different compounds.

Pure Substances

For example…

Two different compounds, each has a definite composition.

Carbon, C Oxygen, O Carbon monoxide, CO

Carbon, C Oxygen, O Oxygen, O Carbon dioxide, CO2

Elements – A Pure Substance

• Cannot be broken down further by chemical or physical methods.

• Elements are organized into the periodic table based on similar properties.

Copper is an element – a pure substance

Compounds – A Pure Substance

• Is made of two or more different elements that are chemically compound.

• Water is a compound made of the elements hydrogen and oxygen.

• Can be broken down into its elements by chemical methods.

• Water can be broken down into hydrogen and oxygen by electrolysis.

-- + -+

Sodium Chloride NaCl – a compound (Salt)

Mixtures

• Contain more than one kind of particle.

• Salt water is a mixture of salt dissolved in water.

• Air is a mixture of gases that include nitrogen, oxygen and carbon dioxide. A granite rock is a

heterogeneous mixture. Notice the different visible parts (minerals).

Mixtures

Variable combination of two or more pure substances. Contain more than one particle.

Heterogeneous Homogeneous

Mixtures

Solution– homogeneous– very small particles

– particles don’t settle– EX: rubbing alcohol

Mixtures

Colloid– heterogeneous– medium-sized particles– particles don’t settle– EX: milk

Mixtures

Suspension– heterogeneous– large particles– particles settle– EX: fresh-squeezed

lemonade

Matter Flowchart

Examples:

– graphite

– pepper

– sugar (sucrose)

– paint

– soda

element

heterogenous mixture

compound

solution Homogenous mixture

heterogenous mixture

Mixtures

Examples:

– mayonnaise

– muddy water

– fog

– saltwater

– Italian salad dressing

colloid

suspension

colloid

solution

suspension

Materials

HomogeneousHeterogeneous

Heterogeneousmixture

Homogeneousmixture

Substance

Element Compound Solution Mixture

Order / Disorder

Smoot, Smith, Price, Chemistry A Modern Course, 1990, page 43

MATTER(gas. Liquid,

solid, plasma)

PURESUBSTANCES MIXTURES

HETEROGENEOUSMIXTURE

HOMOGENEOUSMIXTURESELEMENTSCOMPOUNDS

Separated by

physical means into

Separated by

chemical means into

Kotz & Treichel, Chemistry & Chemical Reactivity, 3rd Edition , 1996, page 31

Elements, Compounds, and Mixtures

(a)an element(hydrogen)

(b)a compound(water)

(c)a mixture(hydrogen and oxygen)

(d)a mixture(hydrogenand oxygen)

Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 68

hydrogenatoms hydrogen

oxygen atoms

Elements, Compounds, and Mixtures

(a)an element(hydrogen)

(b)a compound(water)

(c)a mixture(hydrogen and oxygen)

(d)a mixture(hydrogenand oxygen)

Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 68

hydrogenatoms hydrogen

oxygen atoms

Mixture vs. Compound

Mixture

FixedComposition

Bonds between

components

Can ONLY beseparated by

chemical means

VariableComposition

No bondsbetween

components

Can beseparated by

physical means

Alike Different

Contain two or more

elements

Can beseparated

intoelements

Involvesubstances

Compound

Different

Topic Topic

Compounds vs. Mixtures

• Compounds have properties that are uniquely different from the elements from which they are made. – A formula can always be written for a compound

– e.g. NaCl Na + Cl2

• Mixtures retain their individual properties.– e.g. Salt water is salty and wet

Separating Mixtures

• A filter can separate solids from liquids or gases.

• Distillation can separate liquids in a mixture based on boiling point by vapourization, condensation.

• Magnets will attract iron and steel objects.

Methods of Separating Mixtures

• Magnet

• Filter

• Decant

• Evaporation

• Centrifuge

• Chromatography

• Distillation

Filtration separates

a liquid from a solid

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40

Mixture ofsolid andliquid Stirring

Filtrate (liquidcomponentof the mixture)

Filter papertraps solid

Funnel

Chromatography

• Tie-dye t-shirt

• Black pen ink

• DNA testing– Tomb of Unknown Soldiers– Crime scene – Paternity testing

Setup to heat a solution

Ring stand

Beaker

Wire gauze

Bunsen burner

A Distillation Apparatus

liquid with a soliddissolved in it

thermometer

condenser

distillingflask

pure liquid

receiving flaskhose connected to

cold water faucetDorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 282

The solution is boiled and steam is driven off.

Salt remains after all water is boiled off.

No chemical change occurs when salt water is distilled.

Saltwater solution(homogeneous mixture)

Distillation(physical method)

Pure water

Separation of a sand-saltwater mixture.

Separation of Sand from Salt1. Gently break up your salt-crusted sand with a plastic spoon.

Follow this flowchart to make a complete separation.

Salt-crusted

Wetsand.

Weigh themixture.

Decant clearliquid.

Evaporateto

dryness.

Pour intoheat-resistant

container.

Fill with water.

Stir and letsettle 1 minute.

Weighsand.

Calculateweight of

Repeat3 times?

2. How does this flowchart insure a completeseparation?

Centrifugation

• Spin sample very rapidly: denser materials go to bottom (outside)

• Separate blood into serum and plasma– Serum (clear)– Plasma (contains red blood

cells ‘RBCs’)• Check for anemia (lack of iron)

RBC’s

Before

The decomposition of two water molecules.

2 H2O O2 + 2 H2

Electriccurrent

Watermolecules

Diatomic Diatomicoxygen molecule hydrogen molecules+

Electrolysis

*Must add acid catalyst to conduct electricity

water oxygen hydrogen

“electro” = electricity “lysis” = to split

Hydrogengas forms

Oxygengas forms

ElectrodeSource ofdirect current

H2O(l) O2 (g) + 2 H2 (g)

Electrolysis of Water

Half reaction at the cathode (reduction): 4 H2O + 4 e - 2 H2 + 4 OH 1-

Half reaction at the anode (oxidation): 2 H2O O2 + 4 H 1+ + 4 e -

hydrogengas

cathode

oxygengas

D.C. powersource

Advantages and Disadvantages

• Elements and compounds have positive effects on society such as making our lives healthier and safer.

• Negative consequences – toxic chemicals that are used to produce in the manufacture or isolation of certain elements and compounds can be released into the environment and cause bioaccumulation.

Frog with three legs due to chemical exposure.

ELEMENTELEMENT

hydrogen molecule, H2

ELEMENTELEMENT

oxygen molecule, O2

MIXTUREMIXTURE

a mixture ofhydrogen and oxygen molecules

CHEMICAL REACTIONCHEMICAL REACTION

if molecules collide with enoughforce to break them into atoms, a can take place

COMPOUNDCOMPOUND

water, H2O

2 H22 H2 O2

O2 2 H2O2 H2O++ ++ EE

The Zeppelin LZ 129 Hindenburg catching fire on May 6, 1937 at Lakehurst Naval Air Station in New Jersey.

S.S. Hindenburg

35 people died when the Hindenburg exploded.

May 1937 at Lakehurst, New Jersey

• German zeppelin luxury liner

• Exploded on maiden voyage

• Filled with hydrogen gas

Reviewing ConceptsReviewing ConceptsClassifying Matter

• Why does every sample of a given substance have the same properties?

• Explain why the composition of an element is fixed.

• Describe the composition of a compound.• Why can the properties of a mixture vary?• On what basis can mixtures be classified as

solutions, suspensions, or colloids?• Name two processes used to separate

mixtures?

What’s the Matter Chemistry is the study of matter and the transformations it can undergo…

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